I realize there's going to be a bit of variation here from one author to the next and depending on length of the novel, but the range shouldn't really be too large.

The thing is, I really have no idea where the middle of that range lies. 5,000 words? 10,000? 20,000? I know the average adult vocabulary (in English) ranges between 20,000 and 30,000 words, although I don't know if that number includes variations (like, likes, liked, liking), but I would expect this number to be significantly less than the full breadth of a person's vocabulary.

I had trouble finding any information. Is there anyone who is familiar with this subject?

And the short answer to your good question: IT DEPENDS on a huge range of factors. Any "average" value is likely to be meaningful only for the sample from which it was calculated. You could calculate an NDW for Stephen King novels but that would have little value in making predictions about the work of Umberto Eco.

A concordance of the Bible gives an interesting way to examine some of the issues. (Although this is KJV. I would be interersted to see the differences in GNT.)

While I can't answer the "big" question of an average, I can answer the smaller question of whether anyone's heard/seen anything on the subject before. If anyone has answered a question like this I would assume it would be Franco Moretti or someone doing similar computational research into the statistical profiles of large literary corpora.

Wired did an article on Moretti's research a few years ago. He floats a concept of "distant reading" wherein we cover a lot of ground traditional criticism can't meaningfully cover through statistical methods. I haven't read him widely, so it's possible he's covered this somewhere. I've emailed him before and he was responsive to my questions, though I note from his faculty page that he's on leave this year which may have some effect (as might any pending publications he has on the topic). He also has related books, like Graphs, Maps, Trees & Distant Reading.

This is almost impossible to answer with any degree of accuracy as it depends on so many variables. However, as a very rough and general guide the average novel length is about 80-100,000 words of which about 5-10,000 words would be unique and differentiated.

I'm curious: did you get this data from somewhere?
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J.R.Jan 8 '13 at 9:08

J.R. Yes! But as I said, there's so many variables involved this is just a very rough estimate.
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spiceyokookoJan 9 '13 at 13:28

2

@spiceyokooko - I believe that J.R.'s comment may be asking you to cite those numbers. (I'd also be curious to know where you got them, and what years those numbers represent, since the average novel seems to have gotten longer in the last decade or so.)
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Neil Fein♦Jan 10 '13 at 5:17

New answer just brought me back to this question almost 2 years later. Still not happy with any of the answers, even though I'm itching to accept. Haven't been around much for awhile-- glad to see the beta's still going :)
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AerovistaeNov 24 '14 at 21:26